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    The CachingIterator class

    (PHP 5, PHP 7, PHP 8)

    Introduction

    This object supports cached iteration over another iterator.

    Class synopsis

    class CachingIterator extends IteratorIterator implements ArrayAccess, Countable, Stringable {
    /* Constants */
    public const int CALL_TOSTRING;
    public const int CATCH_GET_CHILD;
    public const int TOSTRING_USE_KEY;
    public const int TOSTRING_USE_CURRENT;
    public const int TOSTRING_USE_INNER;
    public const int FULL_CACHE;
    /* Methods */
    public function __construct(Iterator $iterator, int $flags = CachingIterator::CALL_TOSTRING)
    public function count(): int
    public function current(): mixed
    public function getCache(): array
    public function getFlags(): int
    public function hasNext(): bool
    public function key(): scalar
    public function next(): void
    public function offsetExists(string $key): bool
    public function offsetGet(string $key): mixed
    public function offsetSet(string $key, mixed $value): void
    public function offsetUnset(string $key): void
    public function rewind(): void
    public function setFlags(int $flags): void
    public function __toString(): string
    public function valid(): bool
    /* Inherited methods */
    public function IteratorIterator::current(): mixed
    public function IteratorIterator::getInnerIterator(): ?Iterator
    public function IteratorIterator::key(): mixed
    public function IteratorIterator::next(): void
    public function IteratorIterator::rewind(): void
    public function IteratorIterator::valid(): bool
    }

    Predefined Constants

    CachingIterator::CALL_TOSTRING

    Convert every element to string.

    CachingIterator::CATCH_GET_CHILD

    Don't throw exception in accessing children.

    CachingIterator::TOSTRING_USE_KEY

    Use key for conversion to string.

    CachingIterator::TOSTRING_USE_CURRENT

    Use current for conversion to string.

    CachingIterator::TOSTRING_USE_INNER

    Use inner for conversion to string.

    CachingIterator::FULL_CACHE

    Cache all read data.

    Changelog

    Version Description
    8.0.0 CachingIterator implements Stringable now.

    Table of Contents

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    User Contributed Notes 4 notes

    up
    17
    ahmad dot mayahi at gmail dot com
    6 years ago
    The only difference between CachingIterator and other Iterators such as ArrayIterator is the hasNext() method.

Since the data will be loaded into the memory, the CachingIterator is able to check whether the given iterator has a next element.

Let's demonstrate this by an example:

<?php
$iterator = new CachingIterator(new ArrayIterator(['C', 'C++', 'C#', 'PHP', 'Python', 'Go', 'Ruby']));

foreach ($iterator as $item) {
    if ($iterator->hasNext()) {
        echo $item.', ';
    } else {
        echo 'and '.$item;
    }
}

// C, C++, C#, PHP, Python, Go, and Ruby
?>

In this example I check whether the iterator has a next value, if so, I append a comma otherwise "and" will be appended to the last element.
    up
    9
    ahmad dot mayahi at gmail dot com
    9 years ago
    <?php
//This snippet will print out all the cached elements (foreach) .

$cache  = new CachingIterator(new ArrayIterator(range(1,100)), CachingIterator::FULL_CACHE);

foreach ($cache as $c) {

}

print_r($cache->getCache());
?>
    up
    5
    jerome at chaman dot ca
    6 years ago
    "cached iteration over another iterator" means this iterator is always one step behind the inner iterator. In other words, the "first" iteration will yield null:

<?php

$cit = new CachingIterator( new ArrayIterator( [ 'a', 'b', 'c']  ) );

echo $cit->current() ); // null
echo $cit->getInnerIterator()->current() ); // "a"

while($cit->hasNext()){
    
    // we start with a "next" since the "first" item is null
     $cit->next();
     echo $cit->current(), '<br>';
   
}
?>

iterating this way gives us an access, ahead, to the future item (aka current item of the inner iterator)
    up
    0
    xedin dot unknown at gmail dot com
    6 years ago
    Apparently, the `FULL_CACHE` flag automatically cancels the default flag `CALL_TOSTRING`. This is evident when one of the values cannot be converted to string: with the default `CALL_TOSTRING` flag, it would throw an error; without that flag, or with the `FULL_CACHE` flag, it does not.
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